Image Caption: A blue artificial flower contains sucrose solution in a well in the centre. The flower is placed under a clear Plexiglas table, so the bumblebee (Bombus terrestris) can see the flower, but cannot reach the well with the reward, since the gap between the Plexiglas table and the floor is too small. Hence the bumblebee's only option is to pull the string, until the central well is openly accessible. Here the bumblebee has placed its left front foot on the string to pull it.